To initialize your local repository, use this command:
repo init -u https://github.com/rock-os/manifest.git -b 9.0
Then to sync, use this command:
repo sync -c -j8 --force-sync --no-clone-bundle --no-tags
After download RockOS source now you able to build rom by type
build/envsetup.sh
lunch rockos_CODENAME-userdebug
Then to start build
mka rockos